From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sun, 30 Nov 2014 10:03:31 +0000 (+0800)
Subject: tun: Fix GSO meta-data handling in tun_get_user
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d8febb77b52ebddb9bd03ccaa5b61005e3a45a85;p=linux-beck.git

tun: Fix GSO meta-data handling in tun_get_user

When we write the GSO meta-data in tun_get_user we end up advancing
the IO vector twice, thus exhausting the user buffer before we can
finish writing the packet.

Fixes: f5ff53b4d97c ("{macvtap,tun}_get_user(): switch to iov_iter")
Reported-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 4b743c612624..6d44da184594 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1052,7 +1052,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 
 		if (gso.hdr_len > len)
 			return -EINVAL;
-		iov_iter_advance(from, tun->vnet_hdr_sz);
+		iov_iter_advance(from, tun->vnet_hdr_sz - sizeof(gso));
 	}
 
 	if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {